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/*
MsTimer2.h - Using timer2 with 1ms resolution
Javier Valencia <javiervalencia80@gmail.com>
History:
11/Jun/08 - V0.3
changes to allow working with different CPU frequencies
added support for ATMega128 (using timer2)
compatible with ATMega48/88/168/8
10/May/08 - V0.2 added some security tests and volatile keywords
9/May/08 - V0.1 released working on ATMEGA168 only
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "MsTimer2.h"
unsigned long MsTimer2::msecs;
void (*MsTimer2::func)();
volatile unsigned long MsTimer2::count;
volatile char MsTimer2::overflowing;
volatile unsigned int MsTimer2::tcnt2;
void MsTimer2::set(unsigned long ms, void (*f)()) {
float prescaler = 0.0;
#if defined (__AVR_ATmega168__) || defined (__AVR_ATmega48__) || defined (__AVR_ATmega88__)|| defined (__AVR_ATmega328P__)
TIMSK2 &= ~(1<<TOIE2);
TCCR2A &= ~((1<<WGM21) | (1<<WGM20));
TCCR2B &= ~(1<<WGM22);
ASSR &= ~(1<<AS2);
TIMSK2 &= ~(1<<OCIE2A);
if ((F_CPU >= 1000000UL) && (F_CPU <= 16000000UL)) { // prescaler set to 64
TCCR2B |= (1<<CS22);
TCCR2B &= ~((1<<CS21) | (1<<CS20));
prescaler = 64.0;
} else if (F_CPU < 1000000UL) { // prescaler set to 8
TCCR2B |= (1<<CS21);
TCCR2B &= ~((1<<CS22) | (1<<CS20));
prescaler = 8.0;
} else { // F_CPU > 16Mhz, prescaler set to 128
TCCR2B |= ((1<<CS22) | (1<<CS20));
TCCR2B &= ~(1<<CS21);
prescaler = 128.0;
}
#elif defined (__AVR_ATmega8__)
TIMSK &= ~(1<<TOIE2);
TCCR2 &= ~((1<<WGM21) | (1<<WGM20));
TIMSK &= ~(1<<OCIE2);
ASSR &= ~(1<<AS2);
if ((F_CPU >= 1000000UL) && (F_CPU <= 16000000UL)) { // prescaler set to 64
TCCR2 |= (1<<CS22);
TCCR2 &= ~((1<<CS21) | (1<<CS20));
prescaler = 64.0;
} else if (F_CPU < 1000000UL) { // prescaler set to 8
TCCR2 |= (1<<CS21);
TCCR2 &= ~((1<<CS22) | (1<<CS20));
prescaler = 8.0;
} else { // F_CPU > 16Mhz, prescaler set to 128
TCCR2 |= ((1<<CS22) && (1<<CS20));
TCCR2 &= ~(1<<CS21);
prescaler = 128.0;
}
#elif defined (__AVR_ATmega128__)
TIMSK &= ~(1<<TOIE2);
TCCR2 &= ~((1<<WGM21) | (1<<WGM20));
TIMSK &= ~(1<<OCIE2);
if ((F_CPU >= 1000000UL) && (F_CPU <= 16000000UL)) { // prescaler set to 64
TCCR2 |= ((1<<CS21) | (1<<CS20));
TCCR2 &= ~(1<<CS22);
prescaler = 64.0;
} else if (F_CPU < 1000000UL) { // prescaler set to 8
TCCR2 |= (1<<CS21);
TCCR2 &= ~((1<<CS22) | (1<<CS20));
prescaler = 8.0;
} else { // F_CPU > 16Mhz, prescaler set to 256
TCCR2 |= (1<<CS22);
TCCR2 &= ~((1<<CS21) | (1<<CS20));
prescaler = 256.0;
}
#endif
tcnt2 = 256 - (int)((float)F_CPU * 0.001 / prescaler);
if (ms == 0)
msecs = 1;
else
msecs = ms;
func = f;
}
void MsTimer2::start() {
count = 0;
overflowing = 0;
#if defined (__AVR_ATmega168__) || defined (__AVR_ATmega48__) || defined (__AVR_ATmega88__)|| defined (__AVR_ATmega328P__)
TCNT2 = tcnt2;
TIMSK2 |= (1<<TOIE2);
#elif defined (__AVR_ATmega128__)
TCNT2 = tcnt2;
TIMSK |= (1<<TOIE2);
#elif defined (__AVR_ATmega8__)
TCNT2 = tcnt2;
TIMSK |= (1<<TOIE2);
#endif
}
void MsTimer2::stop() {
#if defined (__AVR_ATmega168__) || defined (__AVR_ATmega48__) || defined (__AVR_ATmega88__) || defined (__AVR_ATmega328P__)
TIMSK2 &= ~(1<<TOIE2);
#elif defined (__AVR_ATmega128__)
TIMSK &= ~(1<<TOIE2);
#elif defined (__AVR_ATmega8__)
TIMSK &= ~(1<<TOIE2);
#endif
}
void MsTimer2::_overflow() {
count += 1;
if (count >= msecs && !overflowing) {
overflowing = 1;
count = 0;
(*func)();
overflowing = 0;
}
}
ISR(TIMER2_OVF_vect) {
#if defined (__AVR_ATmega168__) || defined (__AVR_ATmega48__) || defined (__AVR_ATmega88__)|| defined (__AVR_ATmega328P__)
TCNT2 = MsTimer2::tcnt2;
#elif defined (__AVR_ATmega128__)
TCNT2 = MsTimer2::tcnt2;
#elif defined (__AVR_ATmega8__)
TCNT2 = MsTimer2::tcnt2;
#endif
MsTimer2::_overflow();
}
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